A method of detecting leaks and managing pressure in a fuel system that includes a fuel vapor pressure management apparatus. In particular, a method of detecting leaks and managing pressure in a fuel system that includes a fuel vapor pressure management apparatus that uses naturally forming vacuum to perform a leak diagnostic for a headspace in a fuel tank, a canister that collects volatile fuel vapors from the headspace, a purge valve, and the associated pipes, conduits, hoses, and connections.
Conventional fuel systems for vehicles with internal combustion engines can include a canister that accumulates fuel vapor from a headspace of a fuel tank. If there is a leak in the fuel tank, the canister, or any other component of the fuel system, fuel vapor could escape through the leak and be released into the atmosphere instead of being accumulated in the canister. Various government regulatory agencies, e.g., the California Air Resources Board, have promulgated standards related to limiting fuel vapor releases into the atmosphere. Thus, it is believed that there is a need to avoid releasing fuel vapors into the atmosphere, and to provide an apparatus and a method for performing a leak diagnostic, so as to comply with these standards.
In such conventional fuel systems, excess fuel vapor can accumulate immediately after engine shutdown, thereby creating a positive pressure in the fuel vapor pressure management system. Excess negative pressure in closed fuel systems can occur under some operating and atmospheric conditions, thereby causing stress on components of these fuel systems. Thus, it is believed that there is a need to vent, or xe2x80x9cblow-off,xe2x80x9d the positive pressure, and to vent, or xe2x80x9crelieve,xe2x80x9d the excess negative pressure. Similarly, it is also believed to be desirable to relieve excess positive pressure that can occur during tank refueling. Thus, it is believed that there is a need to allow air, but not fuel vapor, to exit the tank at high flow rates during tank refueling. This is commonly referred to as onboard refueling vapor recovery (ORVR).
The present invention provides a method of using naturally forming vacuum to evaluate a fuel system supplying fuel to an internal combustion engine. The method includes providing a fuel tank including a headspace, coupling in fluid communication the headspace with an intake manifold of the internal combustion engine, a fuel vapor collection canister, a purge valve, and a fuel vapor pressure management apparatus, and detecting the vacuum that naturally forms in the headspace. The fuel vapor management apparatus includes a housing defining an interior chamber, excludes a diaphragm partitioning the interior chamber, and excludes an electromechanical actuator.
The present invention also provides a method of managing pressure in a fuel system supplying fuel to an internal combustion engine. The method includes providing a fuel tank including a headspace, connecting to the headspace an intake manifold of the internal combustion engine, a fuel vapor collection canister, a purge valve, and a fuel vapor pressure management apparatus, and relieving excess pressure that forms in the headspace. The fuel vapor management apparatus includes a housing defining an interior chamber, excludes a diaphragm partitioning the interior chamber, and excludes an electromechanical actuator.
The present invention also provides a method of managing pressure in a fuel system supplying fuel to an internal combustion engine. The method includes providing a fuel tank including a headspace, connecting to the headspace an intake manifold of the internal combustion engine, a fuel vapor collection canister, a purge valve, and a fuel vapor pressure management apparatus, detecting the vacuum that naturally forms in the headspace, and relieving excess pressure that forms in the headspace. The fuel vapor management apparatus includes a housing defining an interior chamber, excludes a diaphragm partitioning the interior chamber, and excludes an electromechanical actuator.
The present invention also provides a method of managing pressure in a fuel system supplying fuel to an internal combustion engine. The method includes providing a fuel tank including a headspace, connecting in fluid communication the headspace to a fuel vapor collection canister, connecting in fluid communication the fuel vapor collection canister to a fuel vapor pressure management apparatus, establishing a fluid flow path extending between the headspace in the fuel tank to atmosphere, relieving excess negative pressure with fluid flow in a first direction along the fluid flow path; and relieving excess positive pressure with fluid flow in a second direction along the fluid flow path. The fuel vapor pressure management apparatus performs leak detection on the headspace, performs excess negative pressure relief on the headspace, and performs excess positive pressure relief on the headspace. The fuel vapor management apparatus includes a housing defining an interior chamber and a pressure operable device. The housing includes first and second ports that communicate with the interior chamber. The pressure operable device separates the interior chamber into a first portion that is in fluid communication with the first port, and a second portion that is in fluid communication with the second port. The establishing the fluid flow path includes passing through the fuel vapor collection canister, passing through the first port, passing through the interior chamber, and passing through the second port. The second direction is opposite to the first direction.
The present invention also provides a method of using naturally forming vacuum to detect leaks in a fuel system supplying fuel to an internal combustion engine. The method includes coupling in fluid communication a headspace of the fuel system to a fuel vapor pressure management apparatus, coupling in electrical communication to the fuel vapor pressure management system an electrical control unit, supplying electrical current to the fuel vapor pressure management system and to the electrical control unit, and performing a leak detection test on the headspace. And the leak detection test draws no more than 100 microamperes of the electrical current.
The present invention also provides a method of using naturally forming vacuum to detect leaks in a fuel system supplying fuel to an internal combustion engine. The method includes coupling in fluid communication a headspace of the fuel system to a fuel vapor pressure management apparatus, and performing with the fuel vapor pressure management apparatus a leak detection test on the headspace. The leak detection test occurs during a period of up to 90 minutes.
The present invention also provides a method of using naturally forming vacuum to detect leaks in a fuel system supplying fuel to an internal combustion engine. The method includes coupling in fluid communication a headspace of the fuel system to a fuel vapor pressure management apparatus, and performing with the fuel vapor pressure management apparatus a leak detection test on the headspace. The leak detection test occurs during a period of at least 20 minutes.